144 THE FAIRY-LAND OF SCIENCE. 
and they, by their rolling to and fro, probably keep 
up the motion and prolong the sound. 
You must not imagine we have explained here the 
many intricacies which occur in the ear; I can only 
hope to give you a rough idea of it, so that you may 
picture to yourselves the air-waves moving (as in Fig. 
34) backward and forward in the canal of your ear, 
then the tympanum vibrating to and fro, the hammer 
hitting the anvil, the stirrup knocking at the little 
window, the fluid waving the fine hairs and rolling 
the tiny stones, the ends of the nerve quivering, and 
then (how we know not) the brain hearing the message. 
Is not this wonderful, going on as it does at every 
sound you hear? And yet this is not all, for inside 
that curled part of the labyrinth g, which looks like a 
snail-shell and is called the cochlea, there is a most 
wonderful apparatus of more than three thousand fine 
stretched filaments or threads, and these act like the 
strings of a harp, and make you hear different tones. 
If you go near to a harp or a piano, and sing any 
particular note very loudly, you will hear this note 
sounding in the instrument, because you will set just 
that particular string quivering, which gives the note 
you sang. The air-waves set going by your' voice 
touch that string, because it can quiver in time with 
them, while none of the other strings can do so. Now, 
just in the same way the tiny instrument of three 
thousand strings in your ear, which is called Corti's 
organ, vibrates to the air-waves, one thread to one set 
of waves, and another to another, and according to 
the fibre that quivers, will be the sound you hear. 
Here then, at last, we see how nature speaks to us. 
